With a rapid development of economic society, a possession quantity of cars in China is growing fast. Road traffic accidents occur frequently, which has become one of important factors that influence public sense of safety. And a problem of traffic safety has become one of basic problems that influence social harmony and improve people's livelihood. China is in urgent need to improve traffic safety from all aspects like technology, policy and education, in which improvement for a design of vehicle safety is an important component.
Technologies of improving vehicle safety can be mainly divided into a passive safety technology and an active safety technology. The passive safety technology is used for protecting people and goods inside and outside a vehicle after an accident. The active safety technology is used for preventing and reducing accidents of the vehicle, so as to prevent people from injury. The active safety technology is focus and trend of the development of modern vehicle safety technology.
By using an advanced wireless communication technology and a new-generation information processing technology, a communication-based collision warning system realizes real-time information interaction between vehicles and between vehicle and roadside infrastructure, informs current states (which may include: position, velocity, acceleration and driving route of each vehicle) and acquired road environment information, collaboratively senses danger conditions of road. Further the communication-based collision warning system also provides timely a variety of collision warning information, so as to prevent the occurrence of road traffic accident. The above has gradually become a new idea for each country to attempt to solve the problem of road traffic safety at present.
Internet of Vehicles refers to provide vehicle information at least one sensor loaded on a vehicle, at least one vehicle terminal and at least one electronic label, and adopt various communication technologies to realize interconnection between vehicles, between vehicle and people, and between vehicle and road. The Internet of Vehicles is used to extract and share information on an information network platform, effectively manage and control vehicles, and provide an integrated service. FIG. 1 is a schematic diagram of sending traffic and scheduling information to a vehicle through a network information platform according to the existing art.
In recent years, with a development of new mobile communication technologies, a research of using a Long Term Evolution (LTE) technology to solve the communication application based on Internet of Vehicles appears in the world.
With the rapid development of Internet and the popularization of multifunctional mobile terminal with large screen, there are a lot of mobile data multimedia services and a variety of high-bandwidth multimedia services, such as video conference, television broadcast, video on demand, advertisement, online education and interactive game. This rapid development not only satisfies the requirement of mobile subscribers for multiple services but also brings mobile operators a new service increasing point. These mobile data multimedia services require multiple subscribers to receive the same data simultaneously. And compared with common data services, the mobile data multimedia services have the characteristics of large volume of data, long duration, and being delay-sensitive.
In order to effectively use mobile network resources, the 3rd Generation Partnership Project (3GPP) puts forward a Multimedia Broadcast Multicast Service (MBMS). This service is a technology of transmitting data from a data source to multiple target mobile terminals, it realizes the sharing of network (including a core network and an access network) resources, and improves the utilization of network resources (especially an air interface resource). The MBMS service defined by 3GPP can not only realize multicast and broadcast of plain-text low-speed messages, but also realize multicast and broadcast of high-speed multimedia services. And the MBMS service provides a variety of video, audio and multimedia services, which assuredly complies with the trend of development of future mobile data, and provides a better service prospect for the development of a 3rd Generation Mobile Technology (3G).
Characteristics of the MBMS service are that the data volume of service is large, the duration of reception of a mobile terminal is long, and average data rate is constant. The above characteristics determine that configurations of both scheduling and control signaling of the MBMS service are semi-static. That is, both scheduling information and control signaling information of the MBMS service remain unchanged for a long time, and this information is sent periodically through an MBMS Control Channel (MCCH) and collectively called MCCH information. There may be multiple MCCHs in an evolved MBMS (eMBMS) system, and each MCCH corresponds to different Multimedia Broadcast Single Frequency Network (MBSFN) areas, and carries control information of the MBMS service sent by the corresponding MBSFN area.
An MBMS notification message is used for describing whether MCCH information changes. A User Equipment (UE) in a Radio Resource Control (RRC) idle mode or an RRC connected mode can get whether the MCCH information changes by monitoring the MBMS notification message, so that selective reception of the MCCH information is realized. That is, when the MCCH information changes, new MCCH information is received. Because the amount of information of the MBMS notification message is much less than that of the MCCH information, the selective reception of the MCCH information of the UE can effectively save resource and reduce power consumption. The MCCH notification message is carried on a Physical Downlink Control Channel (PDCCH) of the specified MBSFN sub-frame and sent periodically. Correspondingly the MBSFN sub-frame and sending period are indicated through a system message (SIB13).
Multiple Multicast Traffic Channels (MTCH) of the MBSFN service and the MCCH of the MBSFN service having the same MBSFN area can be multiplexed on a Multicast Channel (MCH). The MCCH and multiple MTCHs having the same MBSFN area, namely multiple logical channels, can be mapped on the same transmission channel MCH. The MCH can be carried through a transmission block of the MBSFN sub-frame.
An MSAP occasion is also introduced in a MSAP concept, which indicates that in a time period of a dynamic scheduling period, an MCH corresponding to a certain MSAP includes all multicast resources. In the MSAP occasion, multiple MTCHs and dynamic scheduling information can be sent, the MCCH can also be included, and the dynamic scheduling information is carried on a Control Element (CE) of an MAC Protocol Data Unit (PDU). A time length of the MSAP occasion can be 320 ms. The time length of the MSAP occasion is a scheduling period, which is also called a dynamic scheduling period. An MCH can distribute one or more MBSFEN sub-frames in at least one MBSFN frame through the MSAP, in which a sub-frame sent by using a multicast mode is called a MBSFEN sub-frame, and a frame containing the MBSFEN sub-frame is called a MBSFEN frame.
The dynamic scheduling information can be carried on each MSAP occasion configured for an MCH, and carries information of mapping from the MTCH to an assistant MSAP sub-frame. Mapping information is determined by virtue of an index relationship of MBSFN sub-frame numbers in a scheduling period. The UE can get that each MTCH is allocated on which MGSFN sub-frames by reading the scheduling information. Further the UE can read the MTCH of interest on the corresponding MBSFN sub-frame and ignore the MBSFN sub-frame that the UE has no need to read, so that the MBMS service receiving efficiency of the UE is enhanced, and the electrical power consumption of the UE is reduced. The MBSFN sub-frame numbers are determined by using the following way: all the MBSFN sub-frames that are allocated to an MCH in a scheduling period are arranged in a preset order and numbered in order.
An MAC control unit of MCH Scheduling Information (MSI) can be identified through an MAC PDU sub-header carrying a Logical Channel Identifier (LCID). The MAC control unit has a variable length, which is 2x bytes (x is the number of elements in the list MBMS-SessionInfoList). Each MTCH should contain the following domains:
(1) LCID: This domain indicates a logical channel ID of the MTCH, and has a length of 5 bits.
(2) Stop MTCH: This domain indicates a number of the corresponding MTCH end sub-frame in the MSAP occasion, and has a length of 11 bits. The specific stop MTCH value 2047 indicates that the corresponding MTCH is not scheduled, and the values from 2043 to 2046 are reserved.
When a certain MTCH in the MAC PDU does not send, the stop MTCH can be identified by 2047. When all the MTCHs do not have data, the MSI is still sent. If the MSI is not sent (there is an MBMS service indication in the MCCH), the UE considers that there is a failure in the eNB.
By using a characteristic of sending broadcast data to a service area of the MBMS technology, traffic condition, vehicle scheduling information and other information can be sent to an On Board Unit (OBU) in a service area, and vehicle receiving traffic information can select a road to advance.
However, in the current research and practice process, the following problem is provided, which includes that: the UE, which receives the MBMS service of interest, first receives a service notification, and acquires a service identity Temporary Mobile Group Identity (TMGI), service description, start time and other information according to the service notification. Then, the UE monitors an MCCH message, in which the shortest modifying period of the MCCH message is 5.12 seconds. In an environment of Internet of Vehicles, road traffic condition may change suddenly, for example, a traffic accident occurs, at the point, a notification cannot be sent in advance, then the UE cannot acquire the identity TMGI of the service required. Besides, because the time for updating the MCCH is too long, the UE monitors all the MCCH messages, which increases power consumption of the UE. At the same time, the UE cannot acquire needed traffic information.